In thick film conductor systems, copper I oxide is used to promote adhesion to substrates. Copper I oxide powder is added to form chemical or reactive bonds with the substrate, thereby enhancing the adhesion of the conductor.
Known methods of manufacture of copper I oxide involve the furnace reduction of mixtures of copper oxides and copper, the electrolytic process involving plating copper I oxide from an alkaline sodium solution using copper electrodes, or reducing alkaline solutions of copper II salts. These inherently do not produce phase pure copper I oxide. Some copper II oxide is present. This copper II oxide impurity dilutes the efficacy of the copper I oxide and can degrade the solderability of thick film conductors. In addition, these processes are not easily controlled and, therefore, are not found to produce materials with uniform particle size, spherical shape and fully dense, all of which are very important in the improvement in the properties of thick film pastes.
With increasing circuit complexity and decreasing feature sizes, thick film pastes must be composed of pure and chemically uniform particles with very well controlled particle size distributions. Spray pyrolysis has emerged as a promising technique for the production of pure, fully dense, spherical powders with compositional homogeneity at the molecular level with a uniform particle size. Also, the invention may be produced at a lower temperature which produces pure, spherical powders with uniform particle size.